The present invention pertains generally to a pipeline flow stopper. In particular, the present invention pertains to a fully collapsible, inflatable bag-type stopper constructed of an inner airtight bladder encased within an outer fabric casing having sealed seams.
Conventionally, a collapsible, inflatable pipeline flow stopper is constructed of an inner airtight bladder encased within an outer sewn fabric casing. The pipeline flow stopper may be inserted into a pipeline through a small opening tapped in the pipe, commonly known as a tap hole. The pipeline flow stopper may be inserted into the pipeline either by manually pushing it into the tap hole or by using various mechanical devices that facilitate the insertion of the pipeline flow stopper through the tap hole. The purpose of the pipeline flow stopper is to form a temporary obstruction or closure in the pipeline to stop the flow of its contents so that the pipeline can be repaired, replaced, tested or altered in some way.
FIGS. 3 and 4 show two conventional bag-type pipeline flow stoppers comprised of an outer sewn fabric bladder casing having sewn seams. The pipeline flow stopper shown in FIGS. 3(a)-3(b) has a bladder casing 1 constructed from a coated fabric which is cut into the desired shape and stitched together along sewn seams 2. The pipeline flow stopper shown in FIGS. 4(a)-4(c) has a bladder casing la constructed of uncoated fabric which is likewise sewn together along sewn seams 2a. For illustrative purposes, one stopper has a cylindrical shape and the other has a spherical shape, each of which is effective to sealingly engage with the inner peripheral surface of a section of pipeline.
While the prior art pipeline flow stoppers are generally effective to block the major flow of the pipeline contents, they permit, due to their construction, some leakage past the stoppers. The sewn seams 2 and 2a of both types of conventional bladder casings 1 and 1a are disadvantageous because some of the contents, for example, pressurized gas, within the pipeline is able to escape past the sewn seams and the inner bladder. Also, in the case of an uncoated fabric, gas escapes by capillary action through the exposed fibers of the fabric, a phenomenon known as wicking. Furthermore, there is also some leakage between the outside of the stopper, i.e., the outside of the fabric bladder casing and the inside of the pipe wall. Thus, the conventional art has the disadvantage of not providing a fully collapsible pipeline flow stopper that can be inserted into a pipeline through a tap hole and which is leak-proof and which can prevent the flow of any gas past the stopper.
Therefore, there is a need to provide a fully collapsible pipeline flow stopper which can be inserted into a pipeline through a tap hole and which has a bladder casing having a leak-proof construction to prevent any gas from escaping past the stopper.